| PART III.—Current Electricity. | |
| CHAPTER XIV. Construction and Use of Apparatus | [89] |
| [Exp. 101], To study the effect of the electric current uponthe magnetic needle.—Electrical Connections.—CurrentDetectors.—[Exp. 102], To study the construction and useof a simple "key."—[Exp. 103], To study the constructionand use of a simple "current reverser."—[Exp. 104], Tostudy the simple current detector.—[Exp. 105], To studythe construction and use of the simple galvanoscope.—Discussion;True Readings.—[Exp. 106], To study the constructionand use of a simple astatic needle.—AstaticNeedles.—[Exp. 107], To study the construction and useof a simple astatic galvanoscope.—Astatic Galvanoscopes. | |
| CHAPTER XV. Galvanic Cells and Batteries | [102] |
| [Exp. 108], To study the effect of dilute sulphuric acidupon carbon and various metals.—To amalgamate.—Dilutesulphuric acid.—Discussion.—[Exp. 109], To studythe effect of dilute sulphuric acid upon various combinationsof metals.—Discussion.—[Exp. 110], To study theconstruction of a simple Voltaic or Galvanic cell.—TheElectric Current.—Source of the Electrification.—TheElectric Circuit; Open and Closed Circuits.—Plates orElements.—Direction of Current.—Poles or Electrodes.—ChemicalAction in the Simple Galvanic Cell.—Action inCell Using Impure Zinc; Action Using Pure Zinc.—[Exp.111], To see what is meant by "local currents" in thecell.—Local Action; Local Currents.—Reasons for AmalgamatingZinc Plates.—[Exp. 112], To study the "single-fluid"Galvanic Cell.—The Simple Cell.—Polarization ofCells.—Effects of Polarization.—Remedies for Polarization;Depolarizers.—[Exp. 113], To study the "two-fluid"Galvanic Cell.—Setting Up the Two-Fluid Cell.—Care ofTwo-Fluid Cell.—Copper Sulphate Solution.—ChemicalAction in the Two-Fluid Cell.—Various Galvanic Cells;Open and Closed Circuit Cells.—The Leclanché Cell—DryCells.—The Bichromate of Potash Cell.—The DaniellCell.—The Gravity Cell. | |
| CHAPTER XVI. The Electric Circuit | [115] |
| [Exp. 114], To see what is meant by "divided circuits" and"shunts."—Divided Circuits; Shunts.—[Exp. 115], To seewhat is meant by "short circuits." | |
| CHAPTER XVII. Electromotive Force | [117] |
| Electromotive Force.—Unit of E. M. F.; The Volt.—[Exp.116], To see whether the E. M. F. of a cell dependsupon the materials used in its construction.—Discussion.—ElectromotiveSeries.—[Exp. 117], To see whether the E.M. F. of a cell depends upon its size.—Discussion. | |
| CHAPTER XVIII. Electrical Resistance | [120] |
| Resistance.—[Exp. 118], To study the general effect of"resistance" upon a current.—External Resistance;Internal Resistance; Unit of Resistance; The Ohm.—ResistanceCoils; Resistance Boxes.—Simple ResistanceCoil.—[Exp. 119], To test the power of varioussubstances to conduct galvanic electricity.—Conductorsand Nonconductors.—[Exp. 120], To find the effect of sulphuricacid upon the conductivity of water.—InternalResistance.—[Exp. 121], To find what effect the length ofa wire has upon its electrical resistance.—Discussion.—[Exp.122], To find what effect the size (area of cross-section)of a wire has upon its electrical resistance.—Discussion.—[Exp.123], To compare the resistance of adivided circuit with the resistance of one of its branches.Discussion.—[Exp. 124], To study the effect of decreasingthe resistance in one branch of a divided circuit.—Currentin Divided Circuits. | |
| CHAPTER XIX. Measurement of Resistance | [130] |
| [Exp. 125], To study the construction and use of a simpleWheatstone's Bridge.—The Simple Bridge.—EquipotentialPoints.—Example.—[Exp. 126], To measure the resistanceof a wire by means of Wheatstone's Bridge; the"bridge method."—Allowances for Connections.—[Exps.127–137], To measure the resistances of various wires,coils, etc., by the "bridge method."—Table.—[Exp. 138],To study the effect of heat upon the resistance of metals.—Effectof Heat upon Resistance.—[Exp. 139], To measurethe resistance of a wire by the "method of substitution."—SimpleRheostat.—[Exp. 140], To measure the E.M. F. of a cell by comparison with the two-fluid cell.—[Exp.141], To measure the internal resistance of a cellby the "method of opposition." | |
| CHAPTER XX. Current Strength | [142] |
| Strength of Current.—Unit of Current Strength; TheAmpere.—Measurement of Current Strength.—The TangentGalvanometer.—The Ammeter.—The Voltameter.—Unitof Quantity; The Coulomb.—Electrical Horse-power;The Watt.—Ohm's Law.—Internal Resistanceand Current Strength.—[Exp. 142], Having a cell withlarge plates, to find how the strength of the current isaffected by changes in the position of the plates, the externalresistance being small.—[Exp. 143], Same as [Exp.142], but with small plates.—[Exp. 144], To find whetherthe changes in current strength, due to changes in internalresistance, are as great when the external resistance islarge, as they are when the external resistance is small.—Discussion,with examples.—Arrangement of Cells andCurrent Strength.—Cells in Series.—Cells Abreast.—[Exp.145], To find the best way to join two similar cellswhen the external resistance is small.—[Exp. 146], Tofind the best way to join two similar cells when the externalresistance is large.—Best Arrangement of Cells. | |
| CHAPTER XXI. Chemical Effects of the ElectricCurrent | [151] |
| Chemical Action and Electricity.—Electrolysis.—[Exp.147], To study the electrolysis of water.—Compositionof Water.—Electromotive Force of Polarization.—[Exp.148], To coat iron with copper.—[Exp. 149], To study theelectrolysis of a solution of copper sulphate.—Electroplating.—[Exp.150],To study the chemistry of electroplating.—Discussion.—Electrotyping.—Voltameters.—[Exp.151], To study the construction and action of asimple "storage" cell.—Secondary or Storage Cells. | |
| CHAPTER XXII. Electromagnetism | [158] |
| Electromagnetism.—[Exp. 152], To study the lines offorce about a straight wire carrying a current.—Ampere'sRule.—Lines of Force About Parallel Wires.—[Exp. 153],To study the lines of force about a coil of wire like thatupon the galvanoscope.—[Exp. 154], To study the magneticfield about a small coil of wire.—Coils.—Polarity ofCoils.—[Exp. 155], To test the attracting and "sucking"power of a magnetized coil or helix.—[Exp. 156], To findwhether a piece of steel can be permanently magnetizedby an electric current.—[Exp. 157], To study the effect ofa piece of iron placed inside of a magnetized coil of wire. | |
| CHAPTER XXIII. Electromagnets | [165] |
| Electromagnets.—Cores of Electromagnets.—[Exps. 158–163],To study straight electromagnets; Lifting power;Residual magnetism of core; Magnetic tick; Magneticfigures; Magnetic field.—Horseshoe Electromagnets.—Useof Yoke.—Experimental Magnets.—Method ofJoining Coils.—[Exps. 164–173], To study horseshoeelectromagnets; To test the poles; To study the inductiveaction of one core upon the other; Magnetic figures;Permanent Magnetic Figures; Lifting power; Residualmagnetism when magnetic circuit is closed.—Closed MagneticCircuits. | |
| CHAPTER XXIV. Thermoelectricity | [175] |
| [Exp. 174], To find whether electricity can be produced byheat.—Home-made Thermopile.—Thermoelectricity.—PeltierEffect.—Thermopiles. | |
| CHAPTER XXV. Induced Currents | [178] |
| Electromagnetic Induction.—[Exp. 175], To find whethera current can be generated with a bar magnet and ahollow coil of wire.—Discussion.—Induced Currents andWork.—[Exp. 176], To find whether a current can begenerated with a bar magnet and a coil of wire havingan iron core.—[Exp. 177], To find whether a current can begenerated with a horseshoe magnet and a coil of wirehaving an iron core.—Induced Currents and Lines ofForce.—[Exp. 178], To find whether a current can be generatedwith an electromagnet and a hollow coil of wire.—[Exp.179], To find whether a current can be generatedwith an electromagnet and a coil of wire having an ironcore.—Discussion of [Exps. 178]–[179].—[Exp. 180], To studythe effect of starting or stopping a current near a coil ofwire or other closed circuit.—[Exp. 181], To study theeffect of starting or stopping a current in a coil placedinside of another coil.—Discussion of [Exps. 180]–[181].—Directionof Induced Current.—Laws of Induction.—Primaryand Secondary Currents.—[Exp. 182], To see whatis meant by alternating currents.—Direct and AlternatingCurrents.—Self-induction; Extra Currents. | |
| CHAPTER XXVI. The Production of Motion by Currents | [187] |
| Currents and Motion.—[Exp. 183], Motion producedwith a hollow coil and a piece of iron.—[Exp. 184], Motionwith hollow coil and bar magnet.—[Exp. 185], Motion withelectromagnet and piece of iron.—[Exp. 186], Motion withelectromagnet and bar magnet.—[Exp. 187], Motion withelectromagnet and horseshoe magnet.—[Exp. 188], Motionwith two electromagnets.—Discussion of [Exps. 183–188].—[Exp.189], Rotary motion with a hollow coil of wire anda permanent magnet.—[Exp. 190], Rotary motion with anelectromagnet and a permanent magnet.—Discussion of[Exps. 189]–[190]. | |
| CHAPTER XXVII. Applications of Electricity | [192] |
| Things Electricity Can Do.—[Exp. 191], To study theaction of a simple telegraph sounder.—Discussion.—TelegraphLine; Connections.—Operation of Line.—[Exp.192], To study the action of the "relay" on telegraphlines.—The Relay.—[Exp. 193], To study the action of atwo-pole telegraph instrument.—[Exp. 194], To study theaction of a simple "single needle telegraph instrument."—[Exp.195], To study the action of a simple automaticcontact breaker, or current interrupter.—AutomaticCurrent Interrupters.—[Exp. 196], To study theaction of a simple electric bell, or a "buzzer."—ElectricBells and Buzzers.—[Exp. 197], To study the action of asimple telegraph "recorder."—[Exp. 198], To study theaction of a simple "annunciator."—Discussion.—[Exp.199], To study the shocking effects of the "extra current."Induction Coils.—Action of Induction Coils.—Transformers.—TheDynamo.—The Electric Motor.—[Exp. 200],To study the action of the telephone.—The Telephone.—TheBell, or Magneto-transmitter.—The Receiver.—TheCarbon Transmitter.—Induction Coils in TelephoneWork.—Electric Lighting and Heating.—Arc Lamps.—TheIncandescent Lamp. | |
| CHAPTER XXVIII. Wire Tables | [208] |
| APPARATUS LIST | [210] |
| INDEX | [215] |
MAGNETISM
A Few Dont's for Young Students.
Don't fail to make at least a part of your own apparatus; there is a great deal of satisfaction and pleasure in home-made apparatus.
Don't experiment in all parts of the house, if working at home. Fit up a small room for your den, and carry the key.
Don't begin an experiment before you really know what you are trying to do. Read the directions carefully, then begin.
Don't rush through an experiment to see what happens at the end of it. See what happens at each step, and notice every little thing that seems unusual.
Don't try to do all parts of an experiment at the same time. Understand one part, then proceed.
Don't fail to ask yourself questions, and form an opinion about the results of an experiment before you read what the author has to say about it.
Don't fail to keep a note-book. Keep all the data and arithmetical work for future reference.